1. Field of the Invention
The invention concerns a composite material comprising intermetallic phases and ceramic, in particular in the form of a coating on a metallic substrate, as well as an arc wire spraying process for production of the composite material in which the intermetallic phases and the ceramics to be deposited are newly formed during the deposit process from the components of the supplied wires by chemical reaction. The invention further concerns wear resistant layers formed by the composites, tribologic layers and plating or hard-facing materials.
2. Related Art of the Invention
In the production of material layers, the arc wire spraying process or the thermal spray process is characterized by a simple process management and high deposit rate. The coating of components close to their final contours of economical materials by means of arc wire spraying (LDS) satisfies many aspects of the requirements for production of series components and thus is broadly employed in series manufacture applications. The production of thin metallic layers constitutes the state of the art. For each spray pass (coating cycle) layer thicknesses of approximately 0.05 to 0.3 mm are achieved. Greater layer thicknesses must be prepared by multi-layer coating, that is, multiple coating cycles. LDS is one typical process for manufacture of thin layers.
Greater layer thickness, for example the possibility of the manufacture of entire components, can be accomplished by spray compacting by means of thermal spraying. Therein the materials are sprayed as powder or wire in a flame or an arc and processed into semi-finished components.
A disadvantage of the LDS spray layers and the spray compacting for production of layers and semi-finished products are, until now, the insufficient adhesion of the layers to the base material (substrate), the high brittleness, the high porosity and the inhomogeneities of the layers. Particularly disturbing is the tendency towards formation of cracks in thicker layers, that is, greater than 1 mm thickness.
The basic principle of LDS is at the time strongly limited by the selection of materials for formation of the layers, since the wire materials must be electrically conductive, as well as meltable under the process conditions. Thus, primarily only metallic materials are employed, as the case may be, metallic layers are produced. Ceramic high temperature materials are hardly utilizable in this process.
The particularly suited materials include composite materials of metal/ceramic, intermetallic/ceramic (intermetallic phases/ceramic) or intermetallic/metal.
From the Patent DE 198 41 618 C2 an LDS process for production of tribologic coatings of a metal/ceramic composite material for synchronizer rings is known. The wear resistant layer typically contains 40 wt. % TiO2 and the metals Sn, Zn, Cu and/or Al. The porosity is approximately 20%. The deposit of this composite layer occurs preferably by spraying a filled wire comprising a metallic jacket of Cu and/or Al and a filling of TiO2, as well as the metals Sn, Zn, Cu and/or Al. The TiO2 ceramic content of the filled wire and deposited layer remain essentially unchanged. The high hardness with simultaneous high resistance to breakage (ductility) required for wear protective layers, semi-finished products for friction systems or protective platings for ballistic applications is not satisfactorily achieved by these composite materials. Likewise, the porosity is too high.